This invention relates to the coupling of electromagnetic power, such as radiation of a laser, between two waveguides of different cross-sectional dimensions and, more particularly, to a coupler comprising a one-dimensional intermediate waveguide in conjunction with a cylindrical lens disposed between the intermediate waveguide and the larger of the two waveguides, the lens serving to provide a conversion between a cylindrical wavefront and a planar wavefront.
Optical signals may be transmitted by waveguides. By way of example, radiation from a carbon-dioxide laser having a wavelength of 10. 6 microns may be transmitted by a waveguide, such as a rectangular waveguide measuring in the range of approximately two to four millimeters in cross-sectional dimension. In optical systems, the situation may arise wherein it is desired to couple radiant energy from a rectangular waveguide having a first set of cross-sectional dimensions to a second rectangular waveguide having a second set of cross-sectional dimensions different from the dimensions of the first waveguide. For example, it may be desired to couple output power of a carbon-dioxide laser, wherein the output radiation emanates from a square waveguide measuring two millimeters on a side, to a second waveguide of rectangular cross-section measuring two millimeters in height by four millimeters in width. This requires some form of optical coupling structure for converting the waveform of the square waveguide to a waveform suitable for the rectangular waveguide.
A problem arises in that existing coupling structures have excessive complexity, excessive difficulty in alignment, and excessive cost as compared to that which is desirable for providing a suitable waveguide coupler.